Functional contribution of mandibular advancement to awake upper airway patency in obstructive sleep apnea

Abstract

In the narrowed upper airway of patients with obstructive sleep apnea (OSA), a neuromuscular compensatory mechanism augments the activity of the upper airway dilator muscles in defense of upper airway patency, particularly during inspiration. We hypothesized that mechanical enlargement of the upper airway by a mandibular advancement oral appliance would permit a reduction in this neuromuscular compensation during wakefulness. To test this hypothesis, we focused on changes in the cross-sectional (CS) area of the upper airway before and after emplacement of a ventrally titrated oral appliance in 12 awake OSA patients. The CS areas at the end of tidal expiration (CS area-EET) and at the nadir of intraluminal pressure during inspiration (CS area-IN) were obtained using videoendoscopy. The median apnea-hypopnea index decreased with mandibular advancement. Before mandibular advancement, there was no difference between CS area-EET and CS area-IN in the velopharynx, oropharynx, and hypopharynx. This indicates that upper airway dilator muscle activity increased during inspiration to counteract the intraluminal negative pressure of the upper airway. After mandibular advancement, CS area-EET increased in the velopharynx, oropharynx, and hypopharynx, but CS area-IN was unchanged at any level and was less than CS area-EET in the velopharynx and oropharynx. These findings suggest that mandibular advancement enlarges the upper airway and may reduce upper airway dilator muscle activity during inspiration. We conclude that oral appliances act to return the upper airway towards a normal configuration and pattern of muscle function in OSA patients.

Dose-dependent effects of mandibular protrusion on genioglossus activity in sleep apnoea

“…We also found that the cross-sectional area became significantly smaller during inspiration despite mandibular advancement, although the cross-sectional area at end-tidal expiration increased, as expected. We speculated that input from upper airway mechanoreceptors during inspiration decreased phasic GGEMG, since protrusion of the mandible reduced the propensity for upper-airway collapse [5]. Based on the results of the present study and the previous report [5], we can further hypothesise that GGEMG activity could be controlled to maintain a target level of cross-sectional area and patency of the upper airway.…”

“…We speculated that input from upper airway mechanoreceptors during inspiration decreased phasic GGEMG, since protrusion of the mandible reduced the propensity for upper-airway collapse [5]. Based on the results of the present study and the previous report [5], we can further hypothesise that GGEMG activity could be controlled to maintain a target level of cross-sectional area and patency of the upper airway. We recognise that this study merely demonstrates associations, not causality.…”

“…In contrast, if we consider that mandibular advancement increases the cross-sectional area and decreases the propensity for upper airway occlusion, it would be reasonable to hypothesise that a larger, less collapsible upper airway could improve airflow dynamics, which would require less GGEMG [5]. Accordingly, we investigated the effects of mandibular advancement by an experimental oral appliance on GGEMG and the severity of OSA during sleep.…”

“…With the use of an endoscopic technique, we previously demonstrated that the cross-sectional area of the upper airway at end-tidal expiration was maintained during inspiration despite a more negative intraluminal pressure, possibly because of the augmentation of GGEMG in an effort to protect upper airway patency in waking OSA patients [5]. We also found that the cross-sectional area became significantly smaller during inspiration despite mandibular advancement, although the cross-sectional area at end-tidal expiration increased, as expected.…”

Treatment of snoring and sleep apnea syndrome with a removable mandibular advancement device in patients without TMD

“…In advancing the mandible, the splints widen and stretch the muscles, which concurrently produce an increase in electromyographic activity, widening the airway and improving airflow. 1,2,14,17,19,26 Thirteen patients (86.7%) exhibited some degree of tooth sensitivity, especially on awakening in the morning. With splint use, five patients (33%) complained of excessive salivation at night and one patient (6.6%) complained of dry mouth at night.…”